1. Field of the Invention
The present invention relates generally to fluid pumps. More specifically, the invention is a pneumatic pump which includes an air actuator valve mounted in the pump""s reciprocating piston head.
2. Description of Related Art
Prior art pneumatic pumps require an air actuator to control piston cycling. The air actuator is usually mounted on the exterior of the pump and comprises a conglomerate of various parts (screws, diaphragms, spools, o-rings, etc.) which make for a relatively complicated structure that is prone to break down and difficult to repair. A pump which eliminates the need for an externally mounted, complicated air actuator would certainly be a welcome addition to the art.
The relevant art of interest cited herein describes various fluid pumps and actuator valves, but none discloses the present invention. For example, U.S. Pat. No. 5,297,469 (Raymond) describes a power actuator wherein a piston functions as a control valve element. The piston""s position is utilized to generate a signal which triggers a reversing valve. This arrangement employs complicated fluid circuitry.
U.S. Pat. No. 3,963,383 (Hill) discloses an air-driven pump. A shuttle valve for controlling the admission of pressurized air is mounted to the exterior of the pump.
U.S. Pat. No. 4,645,431 (Spencer et al.) shows a piston-driven hydraulic pump wherein the valve for controlling the entrance of pressurized air is mounted to the exterior of the pump.
U.S. Pat. No. 4,120,314 (Lissau), U.S. Pat. No. 4,242,941 (Wilden et al.) and U.S. Pat. No. 6,102,363 (Eberwein) are all drawn to actuator valve structure. The patentees do not contemplate mounting the valves in the head of a piston.
None of the above inventions and patents, taken either singly or in combination, is seen to disclose an injection pump and actuator valve as will subsequently be described and claimed in the instant invention.
The pneumatic fluid injection pump of the instant invention is preferably operated by air. It should be noted that other suitable gases may be utilized if desired. A needle valve which controls the supply of air is disposed in the pump body cap. An air actuator valve is disposed in the piston head. When the pump is in a starting position, the air valve actuator is in a closed position to prevent any passage of air. To start the pumping action, compressed air is fed directly through the pump body cap into the pump body cylinder chamber. The amount of air fed is controlled by the gap between the needle valve and a needle valve seat which is also located in the pump body cap. The air enters the body cylinder chamber and drives the piston and plunger rod through the fluid end of the pump. This action forces the liquid fluid out through a discharge check valve, and simultaneously closes a suction check valve. When the piston is pushed on its pumping stroke, a spring on the air actuator valve contacts a surface of the body cylinder chamber to cause the air actuator valve to open and release the trapped air through the air actuator valve so that the air can exit the pump. This action allows the spring around the piston and plunger to release and return the piston and plunger to the starting position in the body cylinder chamber. This return action causes the liquid to be drawn through the suction check valve into the pump, while simultaneously closing the discharge check valve. When the piston reaches its starting position in the body cylinder chamber, the air actuator valve returns to a closed position, thus allowing the cycle to repeat numerous times per second. The pneumatic injection pump having this internal air valve actuator injects the liquid by positive displacement caused by the reciprocating piston.
Accordingly, it is a principal object of the invention to provide an internal air actuator valve in a fluid injection pump.
It is another object of the invention to provide an internal air actuator valve incorporated in the head of a piston.
It is a further object of the invention to provide an air actuator valve having a compressive spring to elevate the valve upon reaching the end of a piston stroke.
Still another object of the invention is to provide a temporary holding element in the piston head to secure the elevated actuator valve.
It is an object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which are inexpensive, dependable and fully effective in accomplishing their intended purposes.